Fix collections of nullables not being set as nullable (#3364)

* Update to fix Lists/Arrays of nullables not getting marked as nullable

* Updated unit test to cover whether items in a array are correctly marked as nullable or not

* Update src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs

Co-authored-by: Martin Costello <martin@martincostello.com>

* Added some more test cases to unit tests

---------

Co-authored-by: e.kent <e.kent@omcinternational.com>
Co-authored-by: Martin Costello <martin@martincostello.com>

Author: 3 people

src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs

@@ -183,6 +183,10 @@ private OpenApiSchema GenerateSchemaForType(Type modelType, SchemaRepository sch
         if (schema.Reference == null)
         {
             ApplyFilters(schema, modelType, schemaRepository);
+            if (Nullable.GetUnderlyingType(modelType) != null)
+            {
+                schema.Nullable = true;
+            }
         }
 
         return schema;

test/Swashbuckle.AspNetCore.SwaggerGen.Test/SchemaGenerator/JsonSerializerSchemaGeneratorTests.cs

@@ -161,28 +161,34 @@ public void GenerateSchema_GeneratesReferencedDictionarySchema_IfDictionaryTypeI
         Assert.Equal(schema.AdditionalProperties.Reference.Id, referenceSchema.Reference.Id); // ref to self
     }
 
-    public static TheoryData<Type, JsonSchemaType, string> EnumerableTypeData => new()
-    {
-        { typeof(int[]), JsonSchemaTypes.Integer, "int32" },
-        { typeof(IEnumerable<string>), JsonSchemaTypes.String, null },
-        { typeof(DateTime?[]), JsonSchemaTypes.String, "date-time" },
-        { typeof(int[][]), JsonSchemaTypes.Array, null },
-        { typeof(IList), null, null },
+    public static TheoryData<Type, JsonSchemaType, string, bool> EnumerableTypeData => new()
+    {
+        { typeof(int[]), JsonSchemaTypes.Integer, "int32", false },
+        { typeof(int?[]), JsonSchemaTypes.Integer, "int32", true },
+        { typeof(double[]), JsonSchemaTypes.Number, "double", false },
+        { typeof(double?[]), JsonSchemaTypes.Number, "double", true },
+        { typeof(DateTime[]), JsonSchemaTypes.String, "date-time", false },
+        { typeof(DateTime?[]), JsonSchemaTypes.String, "date-time", true },
+        { typeof(IEnumerable<string>), JsonSchemaTypes.String, null, false },
+        { typeof(int[][]), JsonSchemaTypes.Array, null, false },
+        { typeof(IList), null, null, false },
     };
 
     [Theory]
     [MemberData(nameof(EnumerableTypeData))]
     public void GenerateSchema_GeneratesArraySchema_IfEnumerableType(
         Type type,
         JsonSchemaType expectedItemsType,
-        string expectedItemsFormat)
+        string expectedItemsFormat,
+        bool expectedItemsNullable)
     {
         var schema = Subject().GenerateSchema(type, new SchemaRepository());
 
         Assert.Equal(JsonSchemaTypes.Array, schema.Type);
         Assert.NotNull(schema.Items);
         Assert.Equal(expectedItemsType, schema.Items.Type);
         Assert.Equal(expectedItemsFormat, schema.Items.Format);
+        Assert.Equal(expectedItemsNullable, schema.Items.Nullable);
     }
 
     [Theory]